Rafael Nadal's US Open odds have been more than halved after his remarkable win in Cincinnati.

Rafael Nadal's US Open odds have been more than halved after the Spaniard continued his remarkable campaign with the Western & Southern Open title.

After cleaning up on clay, the 27-year-old bounced back from his first-round exit at Wimbledon by maintaining his 100 per recent record on hard court with back-to-back triumphs in Montreal and Cincinnati, leaving him with nine titles from 13 events in 2013.

Sunday's final victory over John Isner also saw him replace Andy Murray as world number two, prompting his odds on ending the year as world number one to plummet to 4/9 with Sky Bet.

Having missed the season's first Grand Slam and dropped down to fifth in the world, Nadal actually drifted out to as long as 16/1 for the end-of-season accolade, while his US Open odds were 7/1 following his SW19 shock loss.

Early exits

However, he has now been cut to joint second favourite with Murray at 5/2, while Novak Djokovic heads the betting at 15/8.

It would be no surprise if we saw Nadal begin as favourite at Flushing Meadows, especially if Murray and Djokovic are placed in the same half of the draw.

Reigning champion Murray was actually installed as favourite after capturing the Wimbledon title but disappointing losses to Ernests Gulbis and Tomas Berdych have tempered expectations somewhat.

The Scot will undoubtedly point to the fact that he also suffered early exits in the two proceeding Masters events last year before capturing his maiden major title, but the shift is more a case of Nadal's form than his own.

Djokovic also disappointed in Montreal and Cincinnati, but far greater concerns lay with Roger Federer's results.

The 17-time Grand Slam champion attempted to switch to a bigger racket following his early exit at Wimbledon but only endured further failings, losing to players outside the top 50 on the clay in Hamburg and Gstaad.

After missing Montreal with a back problem, a return to his trusted racket saw him steady the ship with a quarter-final run in Cincinnati, where he pushed Nadal to three sets.

Only time will tell whether the 32-year-old can really challenge in New York, although Sky Bet are clearly questioning his credentials in offering 11/1 on him landing a sixth title at Flushing Meadows.

The four men to have triumphed at the US Open since Federer's last success are all considered ahead in the betting, with 2009 winner Juan Martin del Potro 10/1.

The towering Argentinian has, however, failed to win either a major or Masters title since that success.

Meanwhile, Victoria Azarenka has been cut from 11/2 to 4/1 after beating Serena Williams in the Cincinnati Masters final, while Maria Sharapova is 7/1 having split with her new coach Jimmy Connors after just one match together.